A high-gain, high-efficiency nonisolated bidirectional DC-DC converter with sustained ZVS operation

This paper proposes a high-gain, highly efficient nonisolated bidirectional DC-DC converter with soft-switching capabilities. An intermediate energy storage cell enables the converter to generate high gain in the continuous current mode. Two auxiliary resonant networks, each consisting of a low-power switch, a capacitor, and an inductor, are integrated to provide the soft switching [zero-voltage switching (ZVS)] for the main switches. The dedicated resonant networks ensure the ZVS is sustained over a wide operating range of duty cycle and power. The auxiliary switches are also soft switched to boost the efficiency further. Additionally, the reverse recovery loss is eliminated by optimizing the resonant capacitors. The validity of the design is verified by a 200 W prototype converter. A maximum gain of 17.8 is observed at a duty cycle ratio of 0.8. At 30 kHz, a full load efficiency of 97.5% and 95.5% is recorded in the boost and buck modes, respectively. On the other hand, at 100 kHz, these efficiencies are 97.0% and 94.5%, respectively. Consequently, the experimental results validate the proposed concept and design procedures. This performance exceeds that of high gain topologies published in the recent literature.